Virological protection of sows upon challenge with Aujeszky's disease virus after multiple vaccinations with attenuated or inactivated vaccines.
The frequency with which sows are vaccinated during eradication programmes has been determined rather arbitrarily in the past, without the necessary scientific support. In the present study the efficacy of repeated vaccinations against Aujeszky's disease virus (ADV) with two inactivated vaccines and with one attenuated ADV-strain (Bartha) suspended in either oil-in-water or saline was evaluated in 40 breeding sows originating from five farms by the assessment of the clinical and virological protection upon an experimental challenge. Sows with two different histories of number of booster vaccinations after a base immunization were selected: young sows which had received 1-3 booster vaccinations and old sows which had received 8-10 booster vaccinations. Two seronegative and two gE-positive sows were included as controls. After challenge, clinical signs such as anorexia and fever were observed in the two seronegative sows and only in four out of the 18 sows which had repeatedly been vaccinated with inactivated vaccines. The mean duration of virus excretion significantly differed (P < 0.05) between the experimental groups. In seronegative sows, virus shedding lasted for 12.5 days. This period was reduced to 6.8-7.9 days in the groups of sows vaccinated with inactivated vaccines having no effect by the number of booster vaccinations and type of vaccine. In the groups of sows vaccinated with Bartha vaccine, challenge virus was detected during 3.7-5.3 days when revaccinated 1-3 times. A reduction to 0.7-1.2 days was obtained with a higher number of boosters (8-10) but only when the vaccine virus was suspended in o/w. Considering the mean cumulative values of virus excretion (area under the curve) it can be stated that sows frequently vaccinated with inactivated vaccines excrete significantly (P < 0.05) higher amounts of virus (26.0-31.5) than sows frequently vaccinated with attenuated ones (1.6-23.7). We may conclude from the present data that the attenuated vaccine virus Bartha, especially when suspended in o/w is superior to inactivated vaccines for inducing clinical and virological protection of sows in the field during their whole breeding period.
Nauwynck
H J
HJ
Laboratory of Veterinary Virology, Faculty of Veterinary Medicine, University of Gent, Merelbeke, Belgium.
Zonnekeyn
V
V
Pensaert
M B
MB
D000818:Animals; D005260:Female; D011558:Herpesvirus 1, Suid / Q000276:immunology*; D007115:Immunization Schedule; D007117:Immunization, Secondary / Q000662:veterinary; D011557:Pseudorabies / Q000517:prevention & control*; D022421:Pseudorabies Vaccines; D013552:Swine; D013553:Swine Diseases / Q000517:prevention & control*; D014613:Vaccines, Attenuated / Q000008:administration & dosage; D015164:Vaccines, Inactivated / Q000008:administration & dosage; D014765:Viral Vaccines / Q000008:administration & dosage
D022421:Pseudorabies Vaccines; D014613:Vaccines, Attenuated; D015164:Vaccines, Inactivated; D014765:Viral Vaccines